(1) Field of the Invention
The present invention relates to a direct-type backlight device and a liquid crystal television apparatus and, more particularly, to a liquid crystal television apparatus employing the direct-type backlight device.
(2) Description of Related Art
Generally, in a display apparatus which is to be viewed away from a screen of the display apparatus, particularly, in a television apparatus or the like, a viewer's attention is prone to be concentrated on a central part of the screen. The viewer is prone to feel that image quality is excellent in a case where the central part of the screen is brighter than a peripheral part of the screen. In the light of this actual situation, the television apparatus is designed such that the peripheral part of the screen becomes dark about 30% as compared to the central part of the screen. Of course, this tendency also applies to a liquid crystal display apparatus and a liquid crystal television apparatus. Therefore, in a liquid crystal display apparatus or a liquid crystal television apparatus which employs a direct-type backlight device, if a backlight in which straight tubes are merely lined up is employed, the viewer is likely to be discontented with image quality.
In order to dissolve the discontent of the viewer, the idea that U-shaped tubes are arranged in face-to-face relationship with one another and raised at central parts thereof, whereby brightness in the central part of the screen is enhanced is previously employed. Moreover, Japanese Patent Application Laid-Open No. 2004-327165 discloses a light emitting device in which fluorescent tubes formed into W-shapes, fluorescent tubes, the number of bending of which is increased, or the like as well as U-shaped tubes are employed, thereby to allow an area in the vicinity of a central part of a light emitting surface of the light emitting device to become bright. Also, Japanese Patent Application Laid-Open No. 2005-347062 discloses a backlight device and a liquid crystal display device in which fluorescent tubes are arranged such that their arrangement spaces in the vicinity of a central area corresponding to a central part of a display screen become narrower than their arrangement spaces in a peripheral area corresponding to a peripheral part of the display screen, or fluorescent tubes in the vicinity of the central part of the display screen are arranged so as to come closer to a diffusion plate as compared with fluorescent tubes arranged at an area positionally corresponding to the peripheral part of the display screen, or a reflector plate having a chevron shape in cross-section which extends along longitudinal directions of the fluorescent tubes is arranged, whereby luminance in an area in the vicinity of the central part of the display screen is enhanced.
In the conventional art, an inverter drive method is realized by employing an inverter for each of the fluorescent tubes or by employing an inverter per two fluorescent tubes connected to each other, thereby constituting a pseudo W-shaped tube, according to the number of the fluorescent tubes to be used. When an inverter is employed for each of the fluorescent tubes, inverter substrates are required on the left and right and the number of inverters to be required is increased. On the other hand, when a pseudo W-shaped tube constituted by two U-shaped tubes is employed, there is a possibility that brightness unevenness is easy to occur in a central part and both ends of the W-shaped tube.
Moreover, in the technology disclosed in Japanese Patent Application Laid-Open No. 2004-327165, the shape of the fluorescent tube is special, so that an increase in cost is not avoided. Also, in the technology disclosed in Japanese Patent Application Laid-Open No. 2005-347062, attention is given to the longitudinal direction of the fluorescent tube but consideration of brightness unevenness in a width direction of the fluorescent tube is not taken.